1. Field of the Invention
The present invention relates to nanoparticles, and particularly to a system and method for producing nanomaterials through an erosion process created by a combination of pressurized fluid and ultrasonic waves focused on a material sample that can be used to form nanoparticles, even from hard materials, such as diamonds.
2. Description of the Related Art
FIG. 4 illustrates a typical fluid jet polishing system 100. System 100 includes a part holder 112, which securely holds a component 113 during the erosion process, within a contained area of an erosion chamber 116. The part holder 112 can be fixed within the erosion chamber 116, rotatable relative to the erosion chamber 116 or form part of a moveable platform. Rotating the part holder 112 facilitates the production of annular or arcuate profiles in the component 113, if desired.
A nozzle 117 directs a pressurized fluid jet stream of a working fluid 118 at a surface of the component 113. The working fluid 118 contains a carrier fluid; e.g. water, glycol, oil or other suitable fluids, and small abrasive particles made from harder materials, such as aluminum oxide, diamond and/or zirconium oxide. Varying the type and size of the abrasive particles can be practiced in order to optimize the surface roughness and/or removal rate. The properties of the working fluid 118, including fluid density, viscosity, pH and rheological properties, can be altered in order to optimize the surface roughness and removal rate. In particular, it is advantageous to have a dilatant fluid in order to increase the removal rate. The viscosity of dilatant fluids increases with increasing shear forces, as compared to normal fluids, in which viscosity is independent of shear forces. Thus, when a fluid jet stream, including a dilatant fluid, impacts on the component 113, the working fluid 118 experiences high shear forces, and therefore has an increase in viscosity, in particular at an interface between the pressurized stream of working fluid 118 and the surface of the component 113.
Abrasive particles that normally have very little effect on the component 113 work much better when a dilatant additive; e.g., corn starch or poly vinyl alcohol, is added. Poly vinyl alcohol is a long chain molecule that can be cross linked to form larger molecules, all with varying degrees of dilatant property. Multiple axis (3, 4, 5 or 6) motion systems may be used to process a wide variety of component shapes. A mechanical linkage 120 may also be added to maintain the angle of the nozzle 117 over spherical or aspheric components 113, and thereby reduce the need for multi-axis motion control systems. During erosion, the end of the nozzle 117 and the component 113 are preferably submerged within the working fluid 118, such that ambient air is not introduced into the closed loop of working fluid slurry. Any air bubbles that are present in the system simply bubble to an air pocket 115 at the top of the erosion chamber 116 and are not re-circulated, thereby producing surfaces with very smooth surface finishes.
The air pocket 115 can be vented continuously or at time intervals. A drain pipe 119 at the bottom of the erosion chamber 116 evacuates the erosion chamber 116 and passes the working fluid 118 with eroded particles from the component 113 to a pump 121, which re-pressurizes the working fluid 118. Plumbing pipes 122 are used to return the working fluid 118 back to the nozzle 117.
A motion system 123, which is typically computer-controlled, e.g., by computer 150, directs the nozzle 117 in the x-y directions, or in any suitable manner (such as three-dimensionally, rotationally, etc.) over the component 113 in accordance with the desired pattern and smoothness on the surface of the component 113. Alternatively, in systems in which the nozzle 117 is fixed and the part holder 112 is movable, the motion system 123 directs the movable platform of the part holder 112 as desired to obtain the required surface shape and roughness.
A property controller 124, including switch 125 and a pair of bypass pipes, may be added to control any one or more of the various properties of the working fluid 118, e.g., temperature, fluid density, viscosity, or pH. If temperature control is required, a temperature sensor in the switch 125 determines the temperature of the working fluid 118 and reroutes all or a portion of the working fluid 118 through the property controller 124 via the bypass pipe, where the temperature of the working fluid 118 is adjusted higher or lower using suitable heating or cooling means. The thermally altered working fluid is passed back to the plumbing 122 via the return bypass pipe. The temperature of the working fluid 118 can be adjusted in order to optimize the removal rate of the component particles and/or the surface roughness of the component 113.
In particle heating or cooling, the tip of the nozzle 117 can affect the properties of the working fluid slurry, thereby increasing or decreasing the removal rate, i.e., cooling the working fluid 118 will lead to a stiffer slurry and an increased removal rate. The property controller 124 can alternatively or also include means for altering the pH of the working fluid 118 by adding high or low pH materials thereto for optimizing the removal rate of component material and the surface roughness of the finished product.
The pump 121 maintains a constant pressure during a single stroke of the fluid jet nozzle 117, and reverses direction after completion of a stroke. The pump 121 includes first and second pumping chambers 132 and 133, respectively, each with a diaphragm 134 and 135 for expanding and/or contracting the volume of the respective pumping chamber 132 and 133. The diaphragms 134 and 135 may be driven electrically, pneumatically or hydraulically. The direction of the pump 121 is coordinated with the fluid jet polishing to ensure that the pressure at the nozzle 117 is constant during a single translation of the nozzle 117 over the workpiece 113.
The pump 121 includes a hydraulic (or pneumatic) actuator pump 137, which drives a hydraulic (or pneumatic) working fluid 139 from the upper part of the first pumping chamber 132, actuating the first diaphragm 134 to expand the volume of the lower part of the first pumping chamber 132. The hydraulic working fluid 139 is forced into the upper part of the second pumping chamber 133, forcing the second diaphragm 135 to contract the volume of the lower part of the second pumping chamber 133, pressurizing and forcing the abrasive fluid 118 through an output conduit 141 to the nozzle 117.
When the hydraulic actuator pump 137 is actuated in the aforementioned direction, a valve assembly 140 is set in a first position (shown in dotted lines) in which the abrasive fluid 118 flows from the drain 119 to the bottom of the first pumping chamber 132, and abrasive fluid 118 flows from the lower part of the second pumping chamber 133 through the output conduit 141 to the nozzle 117. On the next stroke, the hydraulic actuator pump 137 pumps the hydraulic working fluid 139 in the reverse direction, i.e., from the top of the second pumping chamber 133 to the top of the first pumping chamber 132, and the valve assembly 140 ensures that the abrasive fluid 118 flows from the drain 119 to the bottom of the second pumping chamber 133, and from the bottom of the first pumping chamber 132 to the nozzle 117 via the output conduit 141 (shown by solid curved arrows).
The second diaphragm 135 rises to increase the volume of the lower part of the second pumping chamber 133, creating a suction force on the abrasive fluid 118, while the first diaphragm 134 is lowered to decrease the volume of the lower part of the first pumping chamber 132, thereby pressurizing the abrasive fluid 118. Such a typical fluid jet polishing system is shown in U.S. Pat. No. 7,455,573, which is hereby incorporated by reference in its entirety. In such fluid jet polishing systems, the fluid jet stream is highly controllable and produces a controlled polished surface, but the waste products are generally disposed of. Such waste products, however, with some processing, may include valuable materials, and it would be desirable to modify such a fluid jet polishing system to create highly desirable products, such as nanoparticles, from what the polishing system considers as waste.
Thus, a system and method for producing nanomaterials solving the aforementioned problems is desired.